Carburetor



Unite This invention relates to a down draft type carburetor for aninternal combustion engine.

In the carburetor of an internal combustion engine, there is a barrelportion providing a conduit through which atomized fuel and air flow tothe intake manifold. In this conduit or duct there is a throttle valveto control the passage of the gas therethrough.

Along the outside of the conduit of the barrel portion there is achannel for conducting fuel and air mixture to openings through thebarrel wall for passage of the mixture from this channel to the barrelconduit during slow running of the engine. A solid adjusting screw isusually provided to control the passage of mixture into the barrel.

In the conventional type down draft carburetor, the fuel to air ratio isvery high during slow running conditions, and it is very essential tohave good atomization and a homogeneous mixture and to avoid a patchywet mixture which causes excess wear on cylinders and pistons whenstarting a cold engine, also uneven running and waste of fuel under slowrunning conditions.

One of the objects of this invention is to provide a special screw whichmay be substituted for the usual adjusting screw for the slow runningcontrol of the engine to further reatomize the mixture which is beingdrawn from the slow running channel through the opening controlled bythe adjusting screw.

Another object of the invention is to attain smoother running of theengine under slow running conditions due to having a better homogeneousmixture and also to prevent stalling of the engine, which could be verydangerous under road driving conditions.

Another object of the invention is to make starting of the engine easierunder cold weather conditions by reason of further atomization of thefuel.

Another object of the invention is to make the engine States Patent lrespond more sharply to a small movement of the adjusting screw whenmaking idling adjustments to the carburetor.

With these and other objects in view, the invention consists of certainnovel features of construction as will be more fully described andparticularly pointed out in the appended claims.

In the accompanying drawing:

Figure l is a sectional view of the lower portion of a down draftcarburetor;

Figure 2 is a side elevation of my device on a larger scale than thatshown in Figure 1 and separate from installation;

Figure 3 is an end view of Figure 2.

In proceeding with thisinvention, I have provided a screw which may besubstituted for the slow running adjusting screw, usually a part of thecarburetor. I have provided an axial bore from the conical end of theadjusting screw, this axial bore being connected to a series of holesbored transversely through the adjusting screw in such a position as toconnect a passage from the slow running channel to the bore in theadjusting screw when ice fitted in the carburetor. By this arrangementfuel mixture from the slow running channel will partially bypass theconical seating for the adjusting screw.

With reference to the drawing 10 designates the carburetor barrelthrough which there is a conduit 11 for air when the engine is runningslow or for the air and gas mixture to the intake manifold of aninternal combustion engine at high speed. A throttle valve 12 is 1ocatedin this conduit pivoted on the spindle 13 by which a control of theconduit 11 may be provided for. Along the wall 14 of this barrel thereis formed a channel 15 which supplies air and gas mixture, this channelhaving communication with the conduit 11 of the barrel by means ofopenings through the wall 14 at 16, 17, and

' 18. The opening 18 is provided with a conical seat 19 at the entranceend of the opening which is adjacent the channel 15.

A slow running adjusting screw 29 is threaded through a boss 21 of thebarrel at a location where it will cross the channel 15 and is generallycylindrical at 22 but is provided with a tapered or conical end portion23 to engage the seat 19 and close the passage or by reason of its beingslightly open to control the volume of air and gas which may passthrough the opening 18. This slow running adjusting screw is providedwith a handle or head 24 at one end, while at the other end it has anaxially extending bore 25 from its small end inwardly and is alsoprovided with a plurality of radially extending bores 26 extending fromthe cylindrical diameter 22 of the screw inwardly to join the bore 25.The radially extending bores 26, although preferably at a point beyondthe taper 23, may be at any location sufliciently so that the high pointof one of these bores 26 will always be above the seat 19 of the opening18.

A head 24 on the end of the screw provides a convenient handle foroperating the screw, while a spring 27 provides sufiicient tension onthe screw threads so that the adjusting screw will maintain the positionto Which it is adjusted.

The air during slow running will pass as shown by the arrows inwardlythrough opening 16 to channel 15 and back to the conduit 11 throughopenings 17 and 18 and more particularly the gases about the adjustingscrew operate as further described below.

In the functioning of the adjusting screw, the mixture being drawn downthe slow running channel 15 when coming in contact with the channelwalls and conical seat 19 for the adjusting screw 29 has a tendency toliquefy and de-atomize due to the fuel being the heavier part of themixture. During this movement of the mixture the air from the conduitpassing through duct 16 and lighter mixture is partially drawn throughthe bore 25 in the adjusting screw 20. Owing to the orifice of thetransverse holes 26 being at a higher level than the adjusting screwconical seating 19, this lighter mixture, or air, by-passes the conduitbetween the adjusting screw taper 23 and conical seating 19 and passesthrough the center bore 25 of the adjusting screw reatomizing theheavier mixture, or fuel, passing between the conical seatings 19 andcone of the screw 23 into the conduit 11 of the carburetor and ensuringa homogeneous mixture.

The opening between the conical seating 19 and the surface 23 of theadjusting screw is approximately .007 as compared to approximately .015with the conventional type. This condition is due to the fine bore,which is approximately .010", in the adjusting screw which partiallyby-passes a quantity of the slow running mixture, or air and fuel. Thiscondition enables the adjusting screw 20 to have a relatively closerposition to its seating which gives an increased area ratio in relationto the same axial movement of the adjusting screw 20; that is, the arearatio between movements for any small movement of a cone when nearlyclosed is greater than succeeding area ratios for any equal additionalmovement.

This being accomplished, the engine in slow running conditions is muchmore sensitive and responds more quickly for a given movement ofadjusting screw 20. When adjusting the conventional screw, there is atime lapse between movement of the screw to engine response owing to themovement and inertia of the mixture, the tendency when adjusting thecarburetor being to overturn the screw due to delayed response ofengine, making adjustment difiicult for the average individual. With myadjusting screw 20 having an increased ratio in relation to a givenmovement of the screw 20, adjustment is much easier and more accurate,for the adjustment of this screw plays a very important part regardingfuel consumption.

I claim:

1. In a carburetor of the downdraft type a barrel having a conduittherethrough, a throttle valve to control the passage of gases throughsaid conduit, a slow running channel with a wall between it and theconduit having an opening therethrough from the channel to the conduit,an adjusting screw having a portion adjacent but spaced from the wall ofsaid opening for controlling said opening and said adjusting screwhaving a passage therethrough communicating with said conduit and saidchannel at a location in said channel in advance of the portion of theopening controlled by the screw to by-pass some of the controlled gases.

2. In a carburetor as in claim 1 wherein the wall about said opening hasa conical seat and said screw has a conical end to move toward and fromsaid seat to control said opening.

3. In a carburetor as in claim 1 wherein said passage has an axialopening along said screw from the conical end and radial openingsextending therefrom to said channel.

4. In a carburetor as in claim 2 wherein said passage has an axialopening along said screw and radial openings extending therefrom to saidchannel at a location inwardly of the conical seat.

5. In a carburetor as in claim 1 wherein a portion of the passagethrough said screw is at a height above the conical seat.

References Cited in the file of this patent UNITED STATES PATENTS1,761,007 Claudel June 3, 1930 1,781,087 Stapelle Nov. 11, 19301,798,461 Fauser Mar. 31, 1931 2,341,694 Cofiey Feb. 15, 1944 2,590,217Snyder et al. Mar. 25, 1952 FOREIGN PATENTS 363,969 Germany Nov. 16,1922 454,698 Great Britain Oct. 6, 1936

